A piece of iron is heated in a flame. It first becomes dull red then becomes reddish yellow and finally turns to white hot. The correct explanation for the above observation is possible by using

The following four wires are made of the same material. Which of these will have the largest extension when the same tension is applied?

The wettability of a surface by a liquid depends primarily on

A slab of stone of area 0.36 m² and thickness 0.1 m is exposed on the lower surface to steam at 100^oC. A block of ice at 0^oC rests on the upper surface of the slab. In one hour 4.8 kg of ice is melted. The thermal conductivity of slab is
(Given latent heat of fusion of ice = 3.36 $$ \times $$ 10⁵ J kg^$$-$$1)